Stabilized lubricating oil additives



United States Patent STABILIZED LUBRICATING OIL ADDITIVES Walter E. Waddey and Max W. Hill, Westfield, and Elmer B. Cyphers, Cranford, N. 1., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application November 17, 1950, Serial No. 196,362

3 Claims. (Cl. 252-46.7)

The present invention relates to stabilized lubricating oil additives and particularly to sulfur-containing additives such as are used to impart increased film strength and load-carrying capacity to gear lubricants, and the like. The invention relates more broadly to improvements in any type of sulfurized or sulfur-bearing oily products which tend to evolve hydrogen sulfide upon heating or dur ing storage.

As is well known in the prior art, various types of sulfurized and phosphorus sulfide treated organic materials, especially fatty materials, terpenes, esters, phenols, phenol derivatives, olefins and the like, are widely used in the petroleum oil industry to impart improved properties to lubricating oil. They are particularly useful for imparting extreme pressure or improved load-carrying properties and are also widely used to improve resistance to oxidation, metal corrosion, and the like. Many of these products, however, have a highly objectionable tendency to evolve sulfur-containing gases, especially hydrogen sultide, during storage or while in actual use. Aside from the objectionable odor of the sulfur-containing gases, they are frequently quite corrosive and otherwise objectionable in service.

In particular, products such as sulfurized fatty oils, e. g., sulfurized sperm oil and lard oil, and sulfurized fatty materials which have also been treated with a phosphorus compound, are particularly susceptible to the type of deterioration mentioned above. A specific object of the present invention is to reduce the tendency of such products to deteriorate by evolving sulfur-containing gases. e

A specific type of sulfurized fatty oil istbe sulfurized sperm oil or lard oil, or the like, whichis treated, after sulfurization, with a phosphorus sulfide, as in the patent to Cyphers and Osborne, No. 2,498,628. This product has exhibited very useful properties in gearfoils, and the like, to improve their load-carrying performance, but it shows a marked tendency to liberate hydrogen sulfide gas after long storage. It has been suggested previously that the evolution of hydrogen sulfide gas from sulfurized fatty oils, etc., might be inhibited by various treatments. Thus, in the patent to StuckenNo. 2,483,600, the suggestionis made that air may be blown through a sulfurized fatty-oil to remove corrosive products, and in the patent toWatson, No. 2,496,508, it is indicated that the evolution of hydrogen sulfide gas from sulfurized fatty oils' may be prevented by adding organic epoxides. patents sulfurized fatty oils which have been treated with phosphorus sulfide have also been neutralized by treatment with an alkali such as potassium hydroxide. However, the simple neutralization of these sulfurized products apparently is not always suflicient to prevent evolution of His gas. I

Aside from the foregoing, it has been found that in In various prior artthe past attempts to prevent the evolution of sulfur-con- ICE as neutralization withv strong alkali bases, air blowing, etc., which removes active sulfur, tends ordinarily to make these products materially less effective for their intended function. Not only are the extreme pressure additives adversely aflfected, but antioxidants and anticorrosion agents of the sulfur-bearing type, such as sulfurized terpenes, and the like, appear to be reduced in efficiency when treated in the conventional way, e. g. by neutralization with strong alkali bases, etc., to prevent evolution of HzS gas. 7

. According to the present invention, it has been found that products of the type described above may be effectively inhibited against evolution of sulfur-bearing gases without destroying their load bearing effectiveness in lubricants, by treatment with small quantities of relatively strong organic bases. Especially desirable organic bases for this purpose are the amido-imido derivatives of organic acids, for example, guanidine, the diamide imide of ortho carbonic acid, and closely related nitrogen bases. In particular, guanidine, substituted guanidine and guanidine salts of weak acids, such as guanidine carbonates, have been found to be effective treating agents. They reduce greatly, and frequently eliminate entirely, the tendency of sulfurized fatty oils, and the like, to evolve HzS gas while they do not impair, and in some cases they actually improve slightly, the extreme pressure activity of the sulfurized products. They have similar effects on sulfurbearing organic materials used for oxidation inhibition and as corrosion preventives.

EXAMPLE I A sulfurized sperm oil, containing about 6% of sulfur and treated after sulfurization with about 0.5% P483 at a temperature of 215 F. was tested for HzS evolution over a period of 60 days. The test consisted in placing a filter paper moistened with 5% aqueous lead acetate solution over the mouth of a 16 ounce WM square bottle containing the product tested for a period of one minute. The quantity of staining was indicated by a numerical scale, 0 representing no staining and 10 representing a very dark black stain. The odor of H28 is not generally perceptible below a rating of about 7.

The sulfurized sperm oil was tested as indicated below in the table and another sample was treated with a 50% aqueous solution of guanidine carbonate. The guanidine carbonate was used in proportions of 2.5% of the reagent, based on the weight of the P483 treated sulfurized sperm oil. Treatment was effected by adding the guanidine carbonate solution at a temperature of 210 to 220 F. Thereafter, the temperature was increased to 250 F. and maintained for two hours to evaporate the water. After the water was removed, the product was filtered and stored for test. The table below indicates the number of days storage for the respective tests. It will be noted that after 4 days storage the untreated sulfurized sperm oil consistently showed a maximum stain of 10. The products treated with' guanidine carbonate, on the other hand, never reached a rating, higher than 2, even after 60 days storage. V

Table I EFFECT. or GUANIDIN-E CARBONATE TREATMENT 0N H28 EVOLUTION OF Piss TREATED SPERM OIL Dally Lead Acetate Stain Rating 1 Treatment (Days) 1 2 3 4 5 10 15 60 270 None 2.5% Guantdine Carbonate 1 Ratings: 0= no stain; 10=black.

Both the products of Table I were subjected to the standard copper strip test by incorporating 10% of each in a neutral mineral oil of lubricating grade. They were tested on bright copper strips for one hour at 250 F. The untreated product showed a copper strip corrosion rating of 7. The corrosivity of the guanidine carbonate treated material showed a corresponding rating of 4. Both were likewise subjected to the SAE machine test operating at 1,000 R. P. M. Several tests of each product were made and it was found that the untreated material, in 10% solution in lubricating oil, showed a load-bearing rating of 33 on the SAE machine scale. On the other hand, the guanidine carbonate treated material showed an average rating of 63. It is pointed out that the difference between 33 and 63 is not as great, as indicating practical performance, as the numerical difference might suggest, but it is nevertheless a measurable improvement. This was quite unexpected since all previous attempts to prevent H28 evolution had resulted uniformly in a decrease in loadbearing capacity.

EXAMPLE II A sulfurized chlorinated hydrocarbon made by condensing a mixture of chlorowax and chlorokerosene with sodium polysulfide, and containing about 6% sulfur and 30% chlorine, was treated with 2.5% of guanidine carbonate in a 50% aqueous solution, heating and stirring at 250-270 F. for one hour, followed by filtration. This was compared with the untreated material in the H25 test described in Example I. The treated material was almost entirely free of H25 while the untreated material evolved HzS copiously, as shown in Table II, below:

1 Ratings: 0=no stain; =black.

EXAMPLE III A P255 treated barium salt of alkylated phenol sulfide was treated with 2.5% of guanidine carbonate as in Example II, and was also improved in HzS evolution. In this case, the libs evolution at room temperature was only slight in the untreated sample, but this was completely eliminated by the treatment. I n order to demonstrate the improvement more fully in this case, the treated and untreated samples were stored for 24 hours at 140 F. to hasten the evolution of Has. A substantial advantage for the treated sample is shown by the rating of 1+ vs. 5 for the untreated material in this test.

As indicated above, various other strong organic bases of the guanidine or related nitrogenous types may be substituted for guanidine carbonate. The guanidine carbonate, however, is a very desirable reagent. All of these organic nitrogenous bases appear to be preferable to the metallic bases because they make a product which is entirely or substantially free of ash on combustion. For this reason, they are especially useful in crankcase oil compositions for internal combustion engines and in other environments where the oil is partly or largely consumed by combustion when it is desirable to employ a treated additive which is substantially free of metallic or other ash forming constituent.

Although guanidine and its salts are preferred, substituted guanidines may be used. Broadly, the guanidine type basic compounds which may be reacted in accordy .4 ance with the present invention may be defined by the formula N-R Rz'N--Nlh" in which R, R, and R" represent hydrogen or hydrocarbon groups containing 1 to 20 carbon atoms, e. g., straight chain alkyl groups, such as methyl, ethyl, propyl, butyl, also higher straight and branched chain alkyl groups, such as octyl, isooctyl, Z-ethylhexyl, decyl, dodecyl, tetradecyl, cetyl and stearyl radicals. R, R and R may also represent cycloalkyl, arylalkyl, aryl or alkylaryl groups, for example, methylcyclohexyl, phenylethyl, phenyl, cresyl, and tert.-butylphenyl groups. It will be understood that R, R and R" can be the same or different atoms or groups in the same molecule. However, in the case of a substituted guanidine it is most preferable to employ symmetrically tri-substituted compounds, and alkyl and cycloalkyl groups are the more preferred types of substituting groups. These include the symmetrical trialkyl, trinaphthenyl, and triarylalkyl guanidines. Also highly preferred classes of substituted guanidines include the monoalkyl, mononaphthenyl, and monoaralkyl guanidines; unsymmetrical dialkyl, dinaphthenyl, and diarylalkyl guanidines. Somewhat less preferable but still useful classes are the symmetrical dialkyl, dinaphthenyl, and diarylalkyl guanidines, and the mono-, di-, and triaryl guanidines. Still other substituted guanidines may be used, such as biguanide, dicyandiamide, and dicyandiamidine.

The process may be applied to other organic sulfur or phosphorus-sulfur containing compositions, such as thiophosphates, mercaptan derivatives, organic sulfides, polysulfides, and the like, where the evolution of volatile ulfur compounds is a problem. it is applicable also to halogenated sulfur-bearing materials, such as chlorinated waxes, fats and the like which are also treated with sulfur or combined with sulfurized or phospho-sulfurized fats. oils, and related organic materials. In general, proportions of 1 to 5% of the organic base, based on the weight of the sulfur-containing organic material, are to be used. Proportions of 2 to 3% appear to be optimum for sulfurized fatty oils but the proportions obviously may need to be varied somewhat for other organic materials.

While reference has been made above to extreme pressure additives, treated to H28 evolution without substantially injuring their potency as load bearing agents in lubricants, the invention clearly is not restricted thereto. Various organic agents used as oxidation inhibitors, detergents, metal deactivators, corrosion inhibitors, and the like, where active sulfur is present, or where there is any tendency to evolve sulfur-containing gases, may be stabilized in the manner described above. The phenol sulfides and their salts, Xanthates, carbonates, thiophosphates, as well as the sulfurized and phospho-sulfurized hydrocarbons, fats, fatty acids, and the like, previously mentioned appear in general to be susceptible to this treatment. Since these materials are used in lubricating oil, especially mineral base oils and greases, for various purposes, the invention is applicable in general to the sulfur bearing lubricant additives as a class. The invention contemplates the addition of these materials to oils, especially mineral base oils, in normal proportions of 0.01 to 10% or more, for purposes of inhibiting oxidation, giving detergent properties, etc., and especially, in the larger proportions, for conferring extreme pressure properties.

What is claimed is:

1. A process for reducing the tendency of a phosphorus sulfide treated sulfurized sperm oil to evolve hydrogen sulfide on storage which comprises treating said phosphorus sulfide treated sulfurized sperm oil with about 1 to 5% of its weight of guanidine carbonate in aqueous solution at a temperature between about 210 to 300 F. for a time sufficient to reduce its tendency to evolve HzS on storage and to evaporate essentially all of the water, and removing normally solid undissolved constituents therefrom.

2. An improved extreme pressure additive for lubrieating oils consisting essentially of a phosphorus sulfide treated sulfurized sperm oil which has been further treated at an elevated temperature between about 210 to 300 F. with about 1 to 5% of its weight of guanidine carbonate in aqueous solution for a time sufiicient to reduce its tendency to evolve HzS on storage and to remove essentially all of the water, and from which normally solid undissolved constituents have been removed therefrom.

3. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and a minor proportion of the additive defined by claim 2.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR REDUCING THE TENDENCY OF A PHOSPHORUS SULFIDE TREATED SULFURIZED SPERM OIL TO EVOLVE HYDROGEN SULFIDE ON STORAGE WHICH COMPRISES TREATING SAID PHOSPHORUS SULFIDE TREATED SULFURIZED SPERM OIL WITH ABOUT 1 TO 5% OF ITS WEIGHT OF GUANIDINE CARBONATE IN AQUEOUS SOLUTION AT A TEMPERATURE BETWEEN ABOUT 210* TO 300* F. FOR A TIME SUFFICEINT TO REDUCE ITS TENDENCY TO EVOLVE H2S ON STORAGE AND TO EVAPORATE ESSENTIALLY ALL OF THE WATER, AND REMOVING NORMALLY SOLID UNDISSOLVED CONSTITUENTS THEREFORM. 